Development of Placenta

exposure to toxic environment
early cells are pluripotent
no placental connection

first 2 weeks

exposure to toxic environment

• (alcohol, drugs, or infection):

  • Most results in spontaneous abortion

  • A surviving embryo generally develops normally

early cells are pluripotent

• capable of developing into any tissue type; healthy cells replace damaged ones

no placental connection

• the developing zygote is not yet attached to the uterus and does not share the mother's blood supply

third week

• Blastocyst successfully implants into the uterus

• Two layers form: 

  • Inner layer → embryo

  • Outer layer → placenta

• Connection established with the mother's blood supply — embryo receives oxygen and nutrients

embryo
placenta

in the third week two layers form: inner and outer what are these?

blastula

hollow cluster of cells

gastrula

complex layered structure
Generates the three primary germ layers: Ectoderm, Mesoderm, Endoderm

organogenesis

• cells within the three germ layers divide, migrate, and fold into functional organs

gametogenesis

•  primordial germ cells develop from the posterior epiblast and migrate to the developing gonad (mesodermal), alongside the embryonic kidney

gastrulation

process whereby the bilaminar embryonic disc undergoes recognization to form a trilaminar disc

ectoderm

what germ layer
Epithelial tissues: epidermis of the skin; lining of mouth, anus, nasal passages; sweat glands, salivary glands, some mucous glands

• Nervous tissues: brain and spinal cord; peripheral nerves; glial cells (astrocytes, oligodendrocytes, ependymal cells, Schwann cells)

mesoderm

• Epithelial tissues: dermis of the skin; endothelium of blood and lymphatic vessels; mesothelium lining body cavities (peritoneum; pleural and pericardial)

• Connective tissues: cartilage, bone, blood, adipose tissue; fibrous CT (tendons, ligaments); dense CT (dermis, tendons, ligaments); elastic CT (walls of arteries and lungs)

• Muscular tissues: skeletal, smooth, cardiac

endoderm

• Epithelial tissues: lining of the digestive tract (except mouth and anus); lining epithelium of the respiratory tract; epithelial lining of liver and pancreas and other internal organs; urinary bladder; thyroid and parathyroid glands